5-Decyne, also known as dibutylethyne, is a type of alkyne with a triple bond at its fifth carbon (the '5-' indicates the location of the triple bond in the chain). Its formula is C<sub>10</sub>H<sub>18</sub>. Its density at 25 ðC and otherwise standard conditions is 0.766 g/ml. The boiling point is 177 ðC. The average molar mass is 138.25 g/mol.
5-Decyne forms a group of symmetric alkynes with 4-octyne, 3-hexyne, and 2-butyne.